Torque Anchor to Prevent Rotation of Well Production Tubing, System for Pumping and Rotation Prevention, and Pumping Installation Equipped with Such a Torque Anchor

ABSTRACT

The invention relates to a torque anchor which prevents rotation of a tubing string with respect to a casing of a well for pumping a fluid. The torque anchor comprises a frame intended to be mounted in the casing, an internal channel formed in the frame; a cavity in fluid communication with the internal channel, said cavity extending along a radial direction, and an anchoring piston capable of sliding relative to the frame along the radial direction and of exerting torque on the casing, when the pumped fluid contained in the internal channel exerts force on said anchoring piston. The invention also relates to a system for pumping and rotation prevention and a pumping device equipped with such a torque anchor.

RELATED APPLICATIONS

This invention claims priority to French patent application No. FR 14/52171 filed Mar. 17, 2014, the entirety of which is hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to a torque anchor which prevents rotation of a tubing string relative to the casing of a well, and/or a pumping system equipped with a progressive cavity pump comprising such a torque anchor.

BACKGROUND OF THE INVENTION

Torque anchors for a pumping system are known, particularly from document U.S. Pat. No. 6,155,346, which have teeth mounted on a cam fixed to the tubing string. The teeth are displaced by the cam between a retracted position inside the torque anchor and a locking position where the teeth extend radially outward from the frame of the torque anchor and grip the casing.

Such torque anchors have many disadvantages.

First, they are based on bracing technologies, and are therefore likely to become unanchored during production due to the heavy vibrations generated by the progressive cavity pump. This can cause the tubing string to become unscrewed and fall downhole, bringing production to a complete halt and resulting in the significant costs of recovery operations.

Also, in some cases, the retraction mechanism may clog with sand or be affected by corrosion. In this case, the torque anchor is lifted upward by the forces exerted, damaging the casing and the equipment downhole.

In addition, the teeth are brought into locking position by operators using spanners to rotate the tubing string from the surface. This rotation operation poses a hazard to operator safety as they manipulate the spanners to apply torsional stress. When a spanner slips, the operators may be injured.

Moreover, during normal operation, the very principle of the bracing required means an extremely high contact pressure between the teeth and the casing. Thus, given the high level of vibrations during pumping, it is strongly suspected that the teeth, which must necessarily have a destructive shape to initiate the bracing, “machine” the casing.

In addition, some wells are subject to significant temperature variations during production. These temperature variations dilate the tubing string, which can grow by up to 6 meters in length but with little or no expansion in the casing since the casing is cemented to the formation. During these temperature variations, the torque anchor is pushed by the expansion of the tubing, moving it relative to the casing along the longitudinal axis of the well. As the teeth of the torque anchor are always embedded in the casing, some scoring damage to the internal wall of the casing is suspected but has not yet been quantified.

Finally, to ensure that the teeth of the torque anchor are properly gripping the casing, they may be driven into a locking position at the well surface before the torque anchor is lowered downhole. In this case, the casing tube assembly is torn and damaged as the torque anchor is lowered downhole.

Document EP 1,371,810 describes an anti-rotation device of a drilling device. The anti-rotation device is adapted to prevent rotation of the drilling device within the formation being drilled. It comprises pistons able to move radially between a retracted position and an extended position where they extend radially outside the frame and engage with the drilled formation. Movement of the pistons into the extended position is achieved using a hydraulic actuator. A spring returns the piston to the retracted position (FIG. 10, paragraph 183).

However, this anti-rotation device is under-engineered for the torsional forces applied by a stator to the production tubing when the rotor is rotated. The anti-rotation device as described in this document could not withstand such stresses. In addition, the arrangement of the channels transporting pressurized fluid inside the frame to actuate piston movement, is complex to manufacture. Lastly, in case of failure, it would be too expensive to repair or replace a hydraulic pump because this would require emptying the production tubing. The average time between maintenance operations is ten days for a drilling rig, while it is the approximately two years for a fluid pumping system.

In addition, the temperatures in a drill hole are often much higher.

Finally, this anti-rotation device is not suitable for use in a pumping installation equipped with a casing because, in order to anchor the pistons, the pistons must be fitted with sharp teeth which bite into the formation being drilled. Such an anti-rotation device would cut into and damage the casing of the pumping installation. If the pins or teeth are eliminated, the anti-rotation device does not prevent rotation of the production string because the vibrations generated by rotation of the rotor in the stator are very rapid, numerous, and of high amplitude. Damage to the formation being drilled is not an issue because it will later be covered by casing cemented to said formation.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a torque anchor capable of withstanding high torsional moments.

To this end, the invention relates to a torque anchor for preventing rotation of a tubing string relative to a casing of a well for the pumping of a fluid by a progressive cavity pump, said anchor comprising:

-   -   a frame intended to be mounted in the casing,     -   an internal channel formed in the frame, said internal channel         extending along an axial direction;     -   at least one cavity in fluid communication with the internal         channel, said cavity extending along a radial direction, and     -   at least one anchoring piston fitted to said radial cavity,

wherein said anchor comprises at least one pre-loading spring adapted to act between said anchoring piston and the frame to bias said anchoring piston in a radial direction against the casing;

and wherein said internal channel is traversed by the pumped fluid, said anchoring piston being capable of sliding relative to the frame along the radial direction and of exerting torque on the casing, when the pumped fluid contained in the internal channel exerts force on said anchoring piston; said force being a function of the pressure difference between the pressure inside the internal channel and the pressure outside the frame.

Advantageously, the present torque anchor uses the pressure difference between the internal channel and the pressure of the annulus defined between the outer face of the frame and the casing to prevent rotation of the tubing string relative to the casing. This pressure difference is generated by the progressive cavity pump. It can reach several tens of megapascals. The torque anchor can therefore apply very high torque to the inner wall of the casing. In addition, this torque adapts to the clamping torque required since the torque is a function of the pressure difference between the inlet and outlet of the progressive cavity pump. The torque exerted by the torque anchor is automatically controlled by the discharge pressure of the progressive cavity pump.

Advantageously, when there is no pressure difference between the inlet and outlet of the progressive cavity pump, the torque anchor becomes unanchored without any action being required. Therefore, advantageously, the torque anchor cannot become stuck downhole due to sand or scaling.

Advantageously, this torque anchor is compact. In particular, a module having a plurality of pistons within the same plane measures between one and two feet.

Advantageously, this torque anchor can be tested when the torque anchor has been lowered several meters within the casing.

This torque anchor is simple in design. In particular, the anchoring pistons can be easily removed from the frame during a maintenance operation.

According to certain embodiments, the torque anchor comprises one or more of the following features:

The frame comprises a flange facing the periphery of a flat face of the anchoring piston, said flange forming a flat shoulder contained in a plane perpendicular to the radial direction, said at least one pre-loading spring being supported by said shoulder.

Advantageously, the pre-loading spring allows applying torque to the inner wall of the casing when there is no pressure difference between the internal channel and the annulus, for example at the time the rotor is inserted into the stator or at startup of the progressive cavity pump.

The flange forms a wall provided with at least one opening suitable for damping the flow of pumped fluid; said at least opening having a surface area of between 0.5% and 5% of the surface area of a cross-section of the radial cavity; said cross-section being perpendicular to the radial direction.

The frame is subjected to strong vibrations generated by the progressive cavity pump.

Advantageously, restrictor(s) are able to damp the flow of pumped fluid and thereby cushion the frame vibrations.

The frame comprising a sleeve interposed between the radial cavity and the anchoring piston; said sleeve comprising said flange and at least a portion of said flange extending into the internal channel.

Advantageously, this embodiment allows the use of longer springs which are less sensitive to temperature fluctuations and variations in the diameter of the casing, making the performance of the torque anchor more stable.

Said sleeve is made of ceramic.

Advantageously, this equipment eliminates any risk of the anchoring pistons seizing within the sleeve. This equipment also helps to contain the risk of anaerobic corrosion. This embodiment is desirable in applications requiring a long service life or involving high temperatures.

Said anchoring piston comprises a head and a skirt extending the periphery of the head, said head and said skirt forming a chamber that opens to the internal channel; said pre-loading spring being housed in said chamber and guided by said skirt.

Advantageously, the pre-loading springs can be easily removed from the frame during a maintenance operation.

The anchoring piston and the radial cavity have a cylindrical shape with a circular base, the anchoring piston being prevented from rotating relative to the frame by a rotation prevention device.

The rotation prevention device comprises a groove and a tooth able to slide in said groove in a radial direction; one of the groove and tooth being integral to a free end of the skirt and the other to the frame.

A transverse cross-section of the anchoring piston and of the radial cavity has an oblong shape.

Advantageously, this form prevents rotation of the anchoring piston within the radial cavity, with no need for an added dog clutch.

This form also allows increasing the surface area of the piston and therefore the force applied to the casing. Lastly, this form allows increasing the length of the contact with the casing, which reduces the contact pressure and facilitates the passage of casing collars under load.

The anchoring piston has an outer face facing the casing, said outer face being provided with a lip that is preferably rectilinear.

When the anchoring pistons are arranged in a single plane, said lip extends for a distance of between 30% and 70%, and preferably between 30% and 48%, of the inside diameter of the casing, and when the anchoring pistons are arranged in a plurality of planes, the distance defined between the ends of the lips of the end anchoring pistons is between 30% and 70%, and preferably between 30% and 48%, of the inside diameter of the casing.

Advantageously, this length allows the passage of casing collars without damage to the casing.

The torque anchor comprises a gasket ensuring a fluid-tight seal between the anchoring piston and the frame or sleeve.

The torque anchor comprises at least one brace adapted to retain the anchoring piston in a retracted position when the torque anchor is being lowered downhole; said brace being attached on the one hand to a face of the anchoring piston and on the other hand to the frame.

The invention concerns also a system for pumping and preventing rotation of a tubing string relative to a well casing, said system comprising a progressive cavity pump adapted to intake fluid for pumping through an inlet, compress the pumped fluid, and discharge the compressed fluid through an outlet,

wherein the system comprises a torque anchor defined according to the above mentioned features; said torque anchor being secured downstream of the progressive cavity pump, relative to the direction of flow of the fluid pumped within the internal cavity; said torque being a function of the difference in pressure generated by the progressive cavity pump between its inlet and its outlet.

The invention concerns further a pumping installation of a well equipped with a casing; said pumping installation comprising:

-   -   a tubing string arranged in said casing;     -   a progressive cavity pump adapted to move a fluid to be pumped         through an intake inlet, and to discharge the fluid through a         discharge outlet,

wherein the installation comprises a torque anchor defined according to the above mentioned features; said torque anchor being secured downstream of the progressive cavity pump, relative to the direction of flow of the fluid pumped within the internal cavity; said force being a function of the difference in pressure generated by the progressive cavity pump between its inlet and its outlet.

The invention concerns also a method for preventing rotation of a tubing string relative to a casing of a well for pumping fluid by a progressive cavity pump; said method being implemented by a torque anchor comprising a frame intended to be mounted in the casing, an internal channel formed in the frame, said internal channel extending along an axial direction; at least one cavity in fluid communication with the internal channel, said cavity extending along a radial direction, and at least one anchoring piston fitted to said radial cavity, wherein the method comprises the following steps:

-   -   intake of a fluid to be pumped, through an inlet of the         progressive cavity pump,     -   traversal by the pumped fluid of said internal channel,     -   discharge of said pressurized fluid in the tubing string,         through the outlet of said progressive cavity pump;     -   application of pressure by the pumped fluid on a face of the         anchoring piston;

sliding of said anchoring piston relative to the frame in the radial direction; said application causing torque to be applied by said anchoring piston to the casing; said torque being a function of the pressure difference between the and the outlet of the progressive cavity pump.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reading the following description, given only as an example and with reference to the figures, in which:

FIG. 1 is a schematic view of a pumping system according to the present invention;

FIG. 2 is a cutaway perspective view of a torque anchor according to a first embodiment of the invention;

FIG. 3 is an axial sectional view of a portion of the casing and of the torque anchor illustrated in FIG. 1;

FIG. 4 is a graph showing the torque generated by the torque anchor according to the invention as a function of the pressure difference between the inlet and outlet of a progressive cavity pump;

FIG. 5 is a cutaway perspective view of a torque anchor according to a second embodiment of the invention;

FIG. 6 is a sectional view of a portion of the torque anchor illustrated in

FIG. 5, the section plane being perpendicular to an axial axis and passing through a groove of the torque anchor;

FIG. 7 is a cutaway perspective view of a portion of a torque anchor according to a third embodiment of the invention;

FIG. 8 is a sectional view of a portion of the frame and of an anchoring piston representing a variant of the first, second, and third embodiments of the invention;

FIG. 9 is a sectional view of a portion of the frame and of an anchoring piston representing another variant of the first, second, and third embodiments of the invention;

FIG. 10 is a cutaway perspective view of a portion of the frame and of an anchoring piston in a variant of the torque anchor according to the invention;

FIG. 11 is a cutaway perspective view of a torque anchor according to a fourth embodiment of the invention; and

FIG. 12 represents the steps of the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, the terms “top”, “bottom”, “lower”, “upper”, “right”, and “left” are defined relative to the torque anchor according to the invention being arranged as shown in FIG. 1, and are in no way limiting.

The invention relates to a torque anchor and a pumping installation of a well equipped with such a torque anchor.

The pumping installation 2 according to the invention is primarily intended for pumping hydrocarbons, water, or gas. Referring to FIG. 1, it comprises:

-   -   a casing 6 cemented to the formation 7 and comprising         perforations 8 in its lower portion to allow passage of the         fluid to be pumped;     -   a tubing string 10 arranged in the casing 6;     -   a wellhead 12 mounted on a “blowout preventer” 14 and containing         a driving device that rotates the drill string 16 (or one         continuous drill pipe) located inside and extending for the         length of the tubing string 10,     -   a progressive cavity pump 18 having a rotor 20 secured to and         rotated by the drill string 16, and a stator 22 having an intake         opening 24 known as the inlet located downhole, and a discharge         opening 26 known as the outlet fixed at the end of the tubing         string 10,     -   a filter element 28, commonly called a perforated pipe, slotted         screen, or sand screen, attached to the inlet 24 of the         progressive cavity pump, and     -   a torque anchor 30 according to the invention and described         below. The torque anchor 30 is secured downstream of the         progressive cavity pump 18, relative to the direction of flow of         the fluid pumped within the tubing string 10. In the embodiment         represented, the torque anchor 30 is directly fixed to the upper         end of the stator 22. In a variant not represented, thick-walled         tubing called a “blast joint” is attached between the         progressive cavity pump 18 and the torque anchor 30 so that this         tubing is arranged facing the perforations 8 of the casing.

During operation of the progressive cavity pump 18, the fluid contained in the rock moves through the perforations 8 of the casing, and flows into the annulus between the tubing string 10 and casing 6. Then it passes through the slotted screen 28 and into the inlet 24 of the progressive cavity pump.

The progressive cavity pump is composed of a number of cavities defined by the fit between rotor and stator. This fit is called the “seal line.” This seal line generates head loss between each pair of adjacent cavities and thus results in a noticeable difference in pressure between inlet 24 and outlet 26. This pressure difference is usually called the pressure rating.

The fluid is discharged through the discharge outlet 26 in the tubing string 10. The fluid is then advanced to the blowout preventer 14 by the force of the fluid moving in the stator 22, where it is discharged through distribution lines 32. The torque anchor 30 centers and prevents rotation of the pump stator 22 and tubing string 10 during rotation of the rotor 20 of the progressive cavity pump 18. As described below, the torque anchor 30 according to the invention uses the pressure difference generated by the progressive cavity pump 18 to press the anchoring pistons against the inner wall 34 of the casing 6.

Referring to FIGS. 2 and 3, the torque anchor 30 according to the first embodiment of the invention comprises a frame 36, six anchoring pistons 38, 40, 42 supported by the frame, and six pre-loading springs 44, 46, 48 suitable for pushing the anchoring pistons 38, 40, 42 against the casing 6. Note that in the cutaway perspective view of FIG. 2, only five pre-loading springs and three anchoring pistons are visible.

The frame 36, for example generally cylindrical in shape, is provided with an internal channel 50 and six cavities 52, 54, 56, each accommodating one anchoring piston 38, 40, 42 and one pre-loading spring 44, 46, 48. The frame 36 and the internal channel 50 form a section of a pipe.

The internal channel 50 traverses the frame 36 from end to end in an axial direction A-A. It opens onto the flat end walls 58, 60 of the frame. When the torque anchor 30 is mounted in the well, the axial direction A-A is parallel to the longitudinal axis of the shaft and the internal channel 50 is traversed by a drill pipe 62 of the drill string connecting the wellhead to the rotor 20.

The internal channel 50 has a diameter approximately three to four times greater than the diameter of the drill pipe 62 so that the annulus 64 defined between the drill pipe 62 and the internal channel 50 of the frame 36 is sufficient to allow drill string movement caused by eccentricity of the rotor/stator assembly and to allow passage of all the pumped fluid which then rises along the tubing string 10 with no significant head loss.

The radial cavities 52, 54, 56 open to the internal channel 50 and to the outer face 66 of the frame. They radially extend, associated equiangularly, in a plane perpendicular to the axial direction A-A. In the embodiment represented, three radial cavities 52 are arranged in a first plane 68 and the other three radial cavities 54, 56 are arranged in a second plane 70 parallel to the first plane 68. In FIG. 2, only five cavities are visible.

Alternatively, the frame 36 comprises a different number of radial cavities and anchoring pistons in each plane and/or a smaller or greater number of planes.

The radial cavities 52, 54, 56 have a shape complementary to the shape of the anchoring pistons 38, 40, 42. In the embodiment represented, the radial cavities 52, 54, 56 and anchoring pistons 38, 40, 42 have a cylindrical shape with a circular base.

The outer cylindrical face 72 of the anchoring pistons and the inner cylindrical face 74 of the cavities are smooth and continuous. The anchoring pistons 38, 40, 42 can therefore slide out from the frame 36 when biased by the pre-loading springs 44, 46, 48, and under the pressure difference between the pressure of the pumped fluid contained in the internal channel 50 and the pressure in the annulus 75 defined between casing 6 and frame 36. The pressure of the fluid being pumped against the radially sliding anchoring pistons 38, 40, 42 increases the anchoring torque of the torque anchor. This implementation also facilitates removal of pre-loading springs 44, 46, 48 and replacement of anchoring pistons 38, 40, 42 during maintenance operations.

The anchoring pistons 38, 40, 42 are fitted within the radial cavities 52, 54, 56 to allow the anchoring pistons to slide radially while maintaining optimum sealing between frame 36 and anchoring pistons 38, 40, 42. For example, a fit equal to H7 g6 or H6 g5 is used.

The frame 36 comprises a flange 76 extending into each radial cavity 52, 54, 56, opposite a flat face of the anchoring piston. It is integral to the periphery of the inner cylindrical face 74 of the cavities. A flat face of the flange 76 forms a shoulder 78 contained in a plane perpendicular to the radial direction. A pre-loading spring 44, 46, 48 is supported by this shoulder 78.

Preferably, the flange 76 is positioned at the end of the cavity 52 closest to the internal channel 50 to allow using the longest possible pre-loading springs 44, 46, 48.

Alternatively, the flange 76 forms an L-shaped recess of which the lower leg extends into the internal channel 50.

The anchoring pistons 38, 40, 42 comprise a disk-shaped head 80 and a skirt 82 integral with the periphery of the head 80 and extending perpendicularly to the midplane of the head 80.

The head 80 and skirt 82 form a chamber 83 that opens to the internal channel. Each pre-loading spring is housed in a chamber 83. The skirt 82 guides the pre-loading spring 44, 46, 48.

According to this embodiment, the shoulder 78 has a width approximately equal to the thickness of the skirt 82 plus the diameter of the torus formed by the pre-loading spring 44, 46, 48.

The head 80 of each piston has an inner face 84 and an outer face 86 opposite the inner face. The inner face 84 is arranged so that it faces the internal channel 50 when the anchoring piston 38, 40, 42 is mounted in the frame 36. The outer face 86 is arranged so that it faces the casing 6 when the torque anchor 30 is installed in the shaft.

The outer face 86 of the anchoring pistons is provided with a lip or ridge 88 forming a portion of open torus, intended to be pressed against the inner wall 34 of the casing. The cross-section of the lip 88 is preferably rounded so that the lip 88 does not damage the casing 6.

The lip 88 is provided with a coating to increase its wear resistance. The friction coefficient of the coating optimizes its adhesion to the casing. This coating is, for example, based on tungsten carbide or synthetic diamond.

The lip 88 is positioned to form a straight line passing through the center of the outer face 86 of the head. The lip 88 is rounded at the ends to prevent catching during the passage of casing collars. To facilitate lowering the torque anchor 30 within the shaft and to provide maximum resistance to rotation about axis A-A, the anchoring pistons 38, 40, 42 are arranged within the radial cavities 52, 54, 56 so that the lips 88 are positioned parallel to the axial axis A-A.

Alternatively, the lip 88 has a different shape. For example, a serpentine or t-shape will be chosen if it is desired to block both rotation and translation of the torque anchor 30 along and about the axial axis A-A.

The distance D between the end edge of the lip 88 of an anchoring piston 38 located in the first radial plane 68 and the end edge of the lip 88 of the anchoring piston 40 located in the radial plane located at the opposite end (in this case the second radial plane 70) and contained in the same axial plane, is greater than the length of a casing collar so that the torque anchor 30 can traverse the casing collars without damaging them. For example, this distance D is between 30% and 70%, and preferably between 30% and 48%, of the inside diameter of the casing 6.

Alternatively, when the anchoring pistons 38, 40, 42 are arranged in a single plane, the lip 88 of each anchoring piston extends for a length equal to this same distance D, namely a distance D of between 30% and 70%, and preferably between 30% and 48%, of the inside diameter of the casing.

In the first embodiment of the invention, the free end of the skirt 82 is provided with a tooth 90 and the flange 76 located at the foot of the radial cavity comprises a groove 92 in which the tooth 90 is able to slide when the inside diameter of the casing changes and under the pressure of the pumped fluid, as shown in FIG. 3. This dog clutch 90-92 constitutes a rotation prevention device for the anchoring pistons 38, 40, 42 relative to the frame 36 which ensures that the lip 88 remains parallel to the axial axis A-A, in particular when lowering the torque anchor 30 downhole or when the torque anchor 30 vertically shifts within the casing 6 due to temperature variations.

Advantageously, the head 80 of the anchoring piston is reinforced at the lip 88, for example by increasing the size of its cross-section. For example, in the embodiment shown, the cross-section of the head 80 in a plane perpendicular to the lip 88 has a triangular shape, as can be seen in FIG. 6.

The pre-loading springs 44, 46, 48 exert a defined force on the anchoring pistons 38, 40, 42 in the direction of the casing 6, such that the anchoring pistons 38, 40, 42 prevent rotation of the torque anchor 30 when the pressure difference between the pressure of fluid pumped within the internal channel 50 and the pressure in the annulus 75 is low, in other words during startup of the progressive cavity pump 18 or when the amount of pumped fluid is low. The force exerted by the pre-loading springs 44, 46, 48 is dependent on the internal friction torque of the progressive cavity pump 18. It is also lower than the pressure exerted by the pumped fluid, but is sufficient to provide sufficient locking at times when the rotor 20 is not rotating within the stator and therefore is not generating strong vibrations.

The spring constant of the pre-loading springs 44, 46, 48 is calculated to ensure a sufficiently large force to prevent rotation of the tubing string 10 during rotation of the rotor 20, without the threaded connection between the last tube of the tubing string 10 and the torque anchor 30 becoming unscrewed, and without being too high, avoiding damage to the casing 6 or lip 88 when the torque anchor 30 is being lowered downhole.

The pre-loading springs 44, 46, 48 are coil springs. Each is supported by the shoulder 78 at one end and by the inner face 84 of the head at the other.

Alternatively, each anchoring piston 38, 40, 42 comprises a wave spring, or two coil springs mounted coaxially one inside the other preferably with opposite winding directions.

According to a less advantageous variant, the frame comprises one cavity, one anchoring piston housed in said cavity, and one stop. The cavity, anchoring piston, and stop are arranged within the same radial plane 68. The stop extends radially and is placed diametrically opposite the anchoring piston. When the torque anchor is in place in the shaft, the stop and anchoring piston press against the inner face of the casing.

In another variant, the frame comprises one anchoring piston and one cavity in a first radial plane, one anchoring piston and one cavity in a second radial plane, and one anchoring piston and one cavity in a third radial plane. In addition, the cavities and anchoring pistons are distributed equiangularly about the axial axis A-A.

Alternatively, two anchoring pistons contained in two different radial planes are interconnected so that their movements are integral in the radial direction, to facilitate the passage of casing collars under load. This connection may, for example, be achieved by attaching a pin to the teeth 90 of each piston or by attaching a ring of inconel or titanium alloy onto the braces of each anchoring piston head.

During installation of the torque anchor 30 in the shaft, the pre-loading springs 44, 46, 48 and anchoring pistons 38, 40, 42 are inserted into the frame 36 and are retained by a funnel-shaped tool as the torque anchor is inserted into the casing 6 with the tubing string 10. The torque anchor 30 is then lowered downhole. During the lowering of the torque anchor 30 and when the rotor 20 begins to rotate, the pre-loading springs 44, 46, 48 press the anchoring pistons 38, 40, 42 against the casing 6 with minimum torque C1, as illustrated in FIG. 4. Due to its structure, the progressive cavity pump 18 advances the fluid and pushes it into the internal cavity 50 of the torque anchor. Then, the resisting torque applied by the anchoring pistons 38, 40, 42 of the torque anchor increases linearly, ignoring friction, according to the pressure difference between the inlet and outlet of the progressive cavity pump 18. This pressure difference approximately corresponds to the difference in pressure between the pressure in the annulus between the torque anchor 30 and casing 6 and the pressure inside the internal cavity 50. As the pressure generated by the progressive cavity pump 18 is significant, the pressure exerted by the pumped fluid on the anchoring pistons 38, 40, 42 and therefore the force exerted by the anchoring pistons 38, 40, 42 onto the casing 6 is also significant. It can reach several hundred bar.

Thus, advantageously, the torque anchor 30 according to the invention uses the pressure of the displaced fluid to enable or disable anchoring by the torque anchor 30.

Advantageously, the anchoring is automatically controlled by the pressure of the fluid (pressurized pumped fluid or air) contained in the internal channel 50 and therefore by the vibrational state of the tubing string 10 since this state is directly related to the rotational speed of the rotor 20 within the stator 22. It is therefore not necessary to mount a device to control the disabling and enabling of anchoring by the torque anchor 30. Such devices are difficult to implement because they must provide a long service life that can withstand high pressures and high temperatures of up to 200° C.

Referring to FIGS. 5 and 6, the torque anchor 94 according to the second embodiment of the invention is identical to the torque anchor 30 of the first embodiment, except that the flange 76 extends into the radial cavity 52, 54, 56 to form a wall 96 provided with at least one opening 98 suitable for damping the flow of pumped fluid coming from the internal channel 50. The surface area of the opening 98 is about 0.5% to 5% of the surface area of a cross-section of the radial cavity 52, 54, 56, the plane of the cross-section being perpendicular to the radial direction.

The wall 96 is positioned between the internal channel 50 and the radial cavity 52, 54, 56. It narrows the passage between the internal channel and the radial cavity. This narrowing restrictor and the presence of the chamber 83 damps the flow of pumped fluid and thus absorbs the shocks and vibrations to which the torque anchor 94 is exposed. The diameter of the opening 98 is calculated so that it allows enough pumped fluid to pass through to obtain sufficient pressure of the anchoring pistons 38, 40, 42 against the casing 6 while damping the flow of pumped fluid.

In this embodiment, the torque anchor performs an additional function of centering the tubing string relative to the casing and damping the vibrations generated by the progressive cavity pump.

The other technical features of the second embodiment of the invention are identical or similar to the technical features of the first embodiment. They are denoted by the same references and will not be described again here.

Referring to FIG. 7, the torque anchor 100 of the third embodiment of the invention is identical to the torque anchor 30 of the first embodiment except that the frame 36 does not comprise a flange 76 and the frame comprises sleeves 102 interposed between the anchoring pistons 38, 40, 42 and the radial cavities 52, 54, 56.

The sleeves 102 have a shape complementary to the shape of the radial cavities 52, 54, 56. In particular, in the embodiment of the invention represented, the sleeves 102 are in the form of a jacket provided with a flange 76 at one end, extending inwardly into the sleeve. The flange 76 forms a shoulder 78 which supports the pre-loading spring 44, 46, 48.

The sleeves 102 are attached to the hollow inner cylindrical face 74 of the frame defining the radial cavities 52, 54, 56, such that at least a portion of the sleeve 102 provided with its flange 76 is arranged within the internal channel 50.

Advantageously, this attachment is achieved by welding or shrink fitting to ensure a fluid-tight seal.

In the embodiment shown, the flange 76 has a width approximately equal to the thickness of the skirt 82 and the diameter of the torus formed by the pre-loading spring 44, 46, 48.

The sleeve 102 is provided with a groove within which the tooth 90 of the anchoring piston 38, 40, 42 is able to slide.

Advantageously, this embodiment makes it possible to use longer pre-loading springs. This embodiment slightly reduces the cross-section of the passage for the fluid pumped in the internal channel 50.

Preferably, the sleeves are made of Y-TZP zirconia ceramic to eliminate any risk of the pistons jamming as they slide and reduce the risk of premature erosion of the openings 98.

In this embodiment, the frame comprises a supporting surface 103 on which a portion of the sleeve 102 rests. Alternatively, the upper edge of the sleeve located at the external face of the frame may be provided with a flange supported by the frame.

The other technical features of the third embodiment of the invention are identical or similar to the technical features of the first embodiment. They are denoted by the same references and will not be described again here.

Alternatively, the flange 76 extends for a greater length so as to create a restrictor as shown in the embodiment of the invention illustrated in FIG. 5.

According to a variant of the invention, a gasket 104 is provided between the anchoring piston 38, 40, 42 and the frame 36 or sleeve 102.

Referring to FIG. 8, this gasket 104 is arranged in a groove 106 formed in the frame 36 or sleeve 102. In this case, a chamfer 108 is formed on the periphery of the outer cylindrical face 72 of the anchoring piston.

Alternatively and with reference to FIG. 9, a gasket 110 is arranged in a groove 112 formed in the anchoring piston. In this case, a chamfer 114 is formed on the frame 36 along the periphery of the radial cavity 52, 54, 56 or along the inner face of the sleeve 102.

According to a variant represented in FIG. 10, the anchoring pistons 116 and radial cavities 118 have a cylindrical shape with an elliptical base or an oblong cross-section.

The anchoring pistons 116 are formed as a solid block. Two bores 120, 122 are pierced into the inner face 84 of each anchoring piston. The bores 120, 122 extend in a radial direction. A pre-loading spring 44, 46 is arranged in each bore 120, 122.

Preferably, the bores 120, 122 are arranged at each end of the anchoring piston 116. Advantageously, one pre-loading spring 44 is able to retract while the other pre-loading spring 46 is able to extend, when the anchoring piston 116 is in contact with an isolated bump or recess. Alternatively, the two bores 120, 122 are close to each other and are arranged toward the center of the anchoring piston 116.

This alternative form of the anchoring pistons can be used in the four disclosed embodiments of the invention.

Referring to FIG. 11, the torque anchor 124 according to the fourth embodiment of the invention is identical to the torque anchor 100 according to the third embodiment, except that it includes braces 126 adapted to retain the anchoring pistons 38, 40, 42 in a retracted position when the torque anchor 124 is being lowered. The braces 126 are adapted to break off when the torque anchor 124 is in position downhole.

The frame 36 of the torque anchor 124 further comprises a crossbar 128 connecting two diametrically opposed portions of the flange. The brace 126 is attached to the inner face 84 of the anchoring piston and to said crossbar 128 by mating threads 130 or by pins.

The brace 126 is designed to have a sufficiently small diameter for it to break under the pressure of fluid injected into the tubing string by the wellhead.

Alternatively, the frame 36 comprises a hydraulic, electric or acoustic thermal, chemical mechanism able to shear the braces 126 in order to actuate the anchoring springs 44, 46, 48 and achieve the minimum torque C1 necessary to allow insertion of the rotor 20 into the stator 22 without unscrewing the connection between stator 22 and torque anchor 18 or the connection between torque anchor and tubing string.

This embodiment can be implemented with a large opening 98 between the internal cavity 50 and the chamber 83 as illustrated in the first embodiment of the invention, or with a smaller damping opening 98 as in the second embodiment of the invention.

The other technical features of the fourth embodiment of the invention are identical or similar to the technical features of the third embodiment. They are denoted by the same references and will not be described again here.

The invention also relates to a system for pumping and preventing rotation of a tubing string relative to a well casing. The system comprises a progressive cavity pump adapted to intake fluid for pumping through an inlet, compress the pumped fluid, and discharge the compressed fluid through an outlet. This pumping and prevention system comprises a torque anchor according to the invention and as described above. The torque anchor is secured downstream of the progressive cavity pump, relative to the direction of flow of the fluid pumped within the internal cavity. The torque is a function of the difference in pressure generated by the progressive cavity pump between intake and discharge.

In reference to FIG. 12, the invention concerns a method for preventing rotation of a tubing relative to a casing of a shaft for pumping fluid by a progressive cavity pump; said method being implemented by a torque anchor comprising a frame intended to be mounted in the casing, an internal channel formed in the frame, said internal channel extending along an axial direction; at least one cavity in fluid communication with the internal channel, said cavity extending along a radial direction, and at least one anchoring piston fitted to said radial cavity, characterized in that the method comprises the following steps:

-   -   intake (151) of a fluid to be pumped, through an inlet (24) of         the progressive cavity pump (18),     -   traversal (152) by the pumped fluid of said internal channel         (50),     -   discharge (153) of said pressurized fluid in the tubing string         (10), through the outlet (26) of said progressive cavity pump         (18);     -   application (154) of pressure by the pumped fluid on a face of         the anchoring piston (38, 40, 42, 116);     -   sliding (155) of said anchoring piston (38, 40,42,116) relative         to the frame (36) in the radial direction; said application         causing torque to be applied by said anchoring piston (38, 40,         42, 116) to the casing (6); said torque being a function of the         pressure difference between the inlet (24) and the outlet (26)         of the progressive cavity pump.

The present invention also relates to a centering device and/or a damper comprising:

-   -   a frame 36 intended to be mounted in the casing 6,     -   an internal channel 50 formed in the frame, said internal         channel extending along an axial direction (A-A), the pumped         fluid traveling in said internal channel 50;     -   at least one cavity 52, 54, 56, 118 in fluid communication with         the internal channel 50, said cavity 52, 54, 56, 118 extending         along a radial direction, and     -   at least one anchoring piston 38, 40, 42, 116 fitted to said         radial cavity 52, 54, 56, 118, said anchoring piston 38, 40, 42,         116 being capable of sliding relative to the frame 36 along the         radial direction and of exerting torque on the casing 6, when         the pumped fluid contained in the internal channel 50 exerts         force on said anchoring piston 38, 40, 42, 116.

The centering device and/or the damper comprises the features described in relation to FIGS. 5 and 6 and possibly the features described in relation to FIGS. 7 to 11.

Advantageously, the lip 88 of the centering device and/or damper is not coated with tungsten carbide and preferably has a rounded shape.

Advantageously, rotation of the piston within the frame is prevented.

Advantageously, contact of the piston against the inside of the casing is assured.

Advantageously, casing collars are not damaged when lowering the torque anchor to the bottom of the casing. 

1. A torque anchor for preventing rotation of a tubing string relative to a casing of a well for the pumping of a fluid by a progressive cavity pump, said torque anchor comprising: a frame intended to be mounted in the casing, an internal channel formed in the frame, said internal channel extending along an axial direction; at least one cavity in fluid communication with the internal channel, said cavity extending along a radial direction, and at least one anchoring piston fitted to said radial cavity, wherein said torque anchor comprises at least one pre-loading spring adapted to act between said anchoring piston and the frame to bias said anchoring piston in a radial direction against the casing; and wherein said internal channel is traversed by the pumped fluid, said anchoring piston being capable of sliding relative to the frame along the radial direction; said anchoring piston being capable of exerting torque on the casing, when the pumped fluid contained in the internal channel exerts force on said anchoring piston; said force being a function of the pressure difference between the pressure inside the internal channel and the pressure outside the frame.
 2. The torque anchor according to claim 1, wherein the frame comprises a flange facing the periphery of a flat face of the anchoring piston, said flange forming a flat shoulder contained in a plane perpendicular to the radial direction, said at least one pre-loading spring being supported by said shoulder.
 3. The torque anchor according to claim 2, wherein said flange forms a wall provided with at least one opening suitable for restraining the flow of pumped fluid; said at least one opening having a surface area of between 0.5% and 5% of the surface area of a cross-section of the radial cavity; said cross-section being perpendicular to the radial direction.
 4. The torque anchor according to claim 2, wherein the frame comprises a sleeve interposed between the radial cavity and the anchoring piston; said sleeve comprising said flange and at least a portion of said flange extending into the internal channel.
 5. The torque anchor according to claim 4, wherein said sleeve is made of ceramic.
 6. The torque anchor according to claim 2, wherein said anchoring piston comprises a head and a skirt extending the periphery of the head, said head and said skirt forming a chamber that opens to the internal channel, said pre-loading spring being housed in said chamber and guided by said skirt.
 7. The torque anchor according to claim 1, wherein the anchoring piston and the radial cavity have a cylindrical shape with a circular base, the anchoring piston being prevented from rotating relative to the frame by a rotation prevention device.
 8. The torque anchor according to claim 7, wherein the rotation prevention device comprises a groove and a tooth able to slide in the groove in a radial direction, one of the groove and tooth being integral to a free end of the skirt and the other to the frame.
 9. The torque anchor according to claim 1, wherein a transverse cross-section of the anchoring piston and of the radial cavity has an oblong shape.
 10. The torque anchor according to claim 1, wherein the anchoring piston has an outer face facing the casing, said outer face being provided with a lip that is preferably rectilinear.
 11. The torque anchor according to claim 1, wherein, when the at least one anchoring piston is arranged in a single plane, said lip extends for a distance of between 30% and 70%, and preferably between 30% and 48%, of the inside diameter of the casing, and when the at least one anchoring piston comprises a plurality of pistons arranged in a plurality of planes, the distance defined between the ends of the lips of the end anchoring pistons is between 30% and 70%, and preferably between 30% and 48%, of the inside diameter of the casing.
 12. The torque anchor according to claim 5, which further comprises a gasket ensuring a fluid-tight seal between the anchoring piston and the frame or sleeve.
 13. The torque anchor according to claim 1, which comprises at least one brace adapted to retain the anchoring piston in a retracted position when the torque anchor is being lowered downhole, said brace being attached on the one hand to a face of the anchoring piston and on the other hand to the frame.
 14. A system for pumping and preventing rotation of a tubing string relative to a well casing, said system comprising a progressive cavity pump adapted to intake fluid for pumping through an inlet, compress the pumped fluid, and discharge the compressed fluid through an outlet, wherein the system comprises a torque anchor defined according to the features of claim 1, said torque anchor being secured downstream of the progressive cavity pump, relative to the direction of flow of the fluid pumped within the internal cavity, said torque being a function of the difference in pressure generated by the progressive cavity pump between its inlet and its outlet.
 15. A pumping installation of a well equipped with a casing, said pumping installation comprising: a tubing string arranged in said casing; a progressive cavity pump adapted to move a fluid to be pumped through an intake inlet, and to discharge the fluid through a discharge outlet, wherein the installation comprises a torque anchor defined according to the features of claim 1; said torque anchor being secured downstream of the progressive cavity pump, relative to the direction of flow of the fluid pumped within the internal cavity; said force being a function of the difference in pressure generated by the progressive cavity pump between its inlet and its outlet.
 16. A method for preventing rotation of a tubing string relative to a casing of a shaft for pumping fluid by a progressive cavity pump, said method being implemented by a torque anchor comprising a frame intended to be mounted in the casing, an internal channel formed in the frame, said internal channel extending along an axial direction, at least one cavity in fluid communication with the internal channel, said cavity extending along a radial direction, and at least one anchoring piston fitted to said radial cavity, wherein the method comprises the following steps: intake of a fluid to be pumped, through an inlet of the progressive cavity pump; traversal by the pumped fluid of said internal channel; discharge of said pressurized fluid in the tubing string, through the outlet of said progressive cavity pump; application of pressure by the pumped fluid on a face of the anchoring piston; and sliding of said anchoring piston relative to the frame in the radial direction, said application causing torque to be applied by said anchoring piston to the casing, said torque being a function of the pressure difference between the inlet and the outlet of the progressive cavity pump.
 17. A centering device and/or a damper comprising: a frame intended to be mounted in the casing; an internal channel formed in the frame, said internal channel extending along an axial direction, a pumped fluid traveling in said internal channel; at least one cavity in fluid communication with the internal channel, said cavity extending along a radial direction; and at least one anchoring piston fitted to said radial cavity, said anchoring piston being capable of sliding relative to the frame along the radial direction and of exerting torque on the casing, when the pumped fluid contained in the internal channel exerts force on said anchoring piston. 